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. 2019 Apr:57:293-302.
doi: 10.1016/j.mri.2018.12.007. Epub 2018 Dec 20.

Quantification of morphometry and intensity features of intracranial arteries from 3D TOF MRA using the intracranial artery feature extraction (iCafe): A reproducibility study

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Quantification of morphometry and intensity features of intracranial arteries from 3D TOF MRA using the intracranial artery feature extraction (iCafe): A reproducibility study

Li Chen et al. Magn Reson Imaging. 2019 Apr.

Abstract

Background: Accurate and reliable vascular features extracted from 3D time-of-flight (TOF) magnetic resonance angiography (MRA) can help evaluate cerebral vascular diseases and conditions. The goal of this study was to evaluate the reproducibility of an intracranial artery feature extraction (iCafe) algorithm for quantitative analysis of intracranial arteries from TOF MRA.

Methods: Twenty-four patients with known intracranial artery stenosis were recruited and underwent two separate MRA scans within 2 weeks of each other. Each dataset was blinded to associated imaging and clinical data and then processed independently using iCafe. Inter-scan reproducibility analysis was performed on the 24 pairs of scans while intra-/inter-operator reproducibility and stenosis detection were assessed on 8 individual MRA scans. After tracing the vessels visualized on TOF MRA, iCafe was used to automatically extract the locations with stenosis and eight other vascular features. The vascular features included the following six morphometry and two signal intensity features: artery length (total, distal, and proximal), volume, number of branches, average radius of the M1 segment of the middle cerebral artery, and average normalized intensity of all arteries and large vertical arteries. A neuroradiologist independently reviewed the images to identify locations of stenosis for the reference standard. Reproducibility of stenosis detection and vascular features was assessed using Cohen's kappa, the intra-class correlation coefficient (ICC), and within-subject coefficient of variation (CV).

Results: The segment-based sensitivity of iCafe for stenosis detection ranged from 83.3-91.7% while specificity was 97.4%. Kappa values for inter-scan and intra-operator reproducibility were 0.73 and 0.77, respectively. All vascular features demonstrated excellent inter-scan and intra-operator reproducibility (ICC = 0.91-1.00, and CV = 1.21-8.78% for all markers), and good to excellent inter-operator reproducibility (ICC = 0.76-0.99, and CV = 3.27-15.79% for all markers).

Conclusion: Intracranial artery features can be reliably quantified from TOF MRA using iCafe to provide both clinical diagnostic assistance and facilitate future investigative quantitative analyses.

Keywords: Feature measurement; Intracranial artery; Magnetic resonance angiography (MRA); Reproducibility; Stenosis detection.

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Figures

Fig 1
Fig 1
3D visualization of traced arteries in iCafe from two scans of the same subject
Fig 2
Fig 2
(a) M1 segment (indicated by the red bracket) of the Middle Cerebral Artery (MCA) from one of the subjects in this study (b) Traced artery centerlines in green and red lines. The red line indicates the selected M1 segment. Length of M1 segment is calculated as 17.16mm (c) Artery centerlines in green lines and radius estimation for each point along the centerline in blue circles. Volume of M1 segment is calculated as 174.49mm3, average radius is calculated as 1.69mm
Fig 3
Fig 3
Cross-sectional plane (top left) and two perpendicular planes of the cross-sectional plane (top right and bottom) of one of the positions detected by the radiologist but not iCafe (a) and one of the positions detected by iCafe bit not the Radiologist (b). Red cross shows the location of the stenosis position. Stenosis percent of location in (a) is 6.2% calculated from iCafe, below the threshold. Stenosis percent of location in (b) is 12.1% calculated from iCafe, above the threshold.
Fig 4
Fig 4
Bland-Altman plot of the vascular features inter-scan reproducibility. The central dashed line indicates the mean difference and the outer two dashed lines indicate the upper and lower limits of agreement (mean plus 2 times the standard deviation of differences).
Fig 5
Fig 5
Bland-Altman plot of the vascular features intra-operator reproducibility. The central dashed line indicates the mean difference and the two outer dashed lines indicate the upper and lower limits of agreement (mean plus 2 times the standard deviation of differences).
Fig 6
Fig 6
Bland-Altman plot of the vascular features inter-operator reproducibility. The central dashed line indicates the mean difference and the two outer dashed lines indicate the upper and lower limits of agreement (mean plus 2 times the standard deviation of differences).

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